An element which is a meter long and 2KWatt, or 300mm long and 2Kwatt, will still produce the same amount of heating energy, the only difference, is that the temperature along the longer element may be less at the surface area than the shorter element, BUT this does not mean that the shorter element is more efficient in heating the water than the longer element, what it would do, if you were using it to heat barley or some other organic material, is to burn on the surface of the shorter element any organic material. Water is not organic, and therefor makes no difference at what temperature is on the surface of the element, the heat will be absorbed by the water, and will pass on to the cooler parts of the geyser, thereby equalizing the total temperature through out the vessel. If there are temperature differences, then this would be due to lost heat to the environment at the points where the temperature is lower.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
I'm not an expert on Kwikot 150 litre geysers but I will be in the next few days because I have an old one in my workshop that was left in the roof space by the bone idle lazy plumbers who replaced it under warranty last year and the first time I get a chance it will be disected on my workbench.
Reading between the lines here I'm guessing the big metal plate you're referring to may be an internal baffle inside the cylinder perhaps.
Any components inside the cylinder, including any metal plates, will have heat losses but those losses are determined by two things, the temperature difference between the internal cylinder and the surrounding environment and the quality of the insulation that surrounds the cylinder.
If there is an internal baffle plate then altering the length of the element could have a profound effect on the circulation of the water inside the geyser whilst it's being heated. It could have an effect on the temperature gradient between water at the bottom of the cylinder and water at the top. It could even result in a large percentage of the water in the cylinder remaining cold or cool due to lack of circulation during heating.
Regardless of the numerous possibilities one thing is certain, if the geyser is consuming less electricity with the new element arrangement then it's producing less hot water. Yes, the water that comes out when a tap is turned on may be at the same temperature that it was with the old element but there will be less of it available so during high demand times the geyser water will become cold sooner. You're effectively taking a 150litre geyser and turning it into one that only produces 120 litres or maybe 100 litres of hot water. Could it produce electricity savings? Maybe it could but I still doubt it would be even remotely close to the 40% claims and if its a family of four or five people there's a good chance a couple of them will be taking cold showers.
However you wiggle and jiggle the element in a geyser, any savings will be at a cost, you'll always end up robbing Peter to pay Paul.
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Thank you all for the active feedback. I am not yet certain of the savings and we are doing field tests. Once complete I will share the results either way. Signing off until I have more information back from the field. We will not be selling this to a soul if the evidence in the field does not continue to back up the numbers from the lab.
WRT to the last point about less hot water, the lab tests include emptying the geyser and measuring the the average water temperature to add back/subtract from the other power measurements for remaining energy in the geyser. I will bug you all no more until I have more numbers.
It would be worthwhile to log all data, i.e. ambient and internal water temperature, energy used / consumed, and water disposed / re-filled during the test periods.
Hi Again
We have just launched this product to market. Please see www.econocoilsa.co.za for the test reports and video. I know there are many skeptics borne of many unfulfilled promises of efficiency.
I would value your expert feedback on our information.
Our field tests delivered an average of 33% saving. This was in 5 separate homes. We measured water flow through the geyser and power using an effergy meter on the element line. The tests were done for 2-4 weeks with the standard element & Econocoil.
I look forward to taking heat from you again!
Cheers
Rich
None of the links on the website to the Skeg full 20 page report work, I tried Firefox and Opera so I'm guessing it's a website technical issue.
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Thanks Andy. Dumb error on website. Thank you for picking it up. It is now fixed.
I still don't understand how this element can save this much electricity. As many posts have mentioned, Q=mCp(T1-T2), so heating m litres of water by y degrees will require a defined amount of energy. The only variable will be the heat losses.
The website states that the energy saving is achieved by mixing the water inside the geyser more efficiently, dropping the temperature in the top section by say 20 deg, which then leads to lower heat transfer. I agree, and a quick calculation will show that the reduced heat flow of an insulated section at 60 deg vs 80 deg is about 28%. But then the temperature of the whole geyser is higher, and losses will be higher over the entire surface of the cylinder, not just the top section. So I suspect savings are not very significant.
Heat loss depends totally on the insulation of the geyser tank and the temperature of the surrounding air. Geysers manufactured to SABS standards are controlled in terms of their standing heat loss and the insulation requirements are regulated by SANS 151. The maximum allowable heat loss for a 150lt capacity geyser (most common geyser size) is 2.6kW per 24 hours at a stored water temperature setting at 65 degrees C and no water is drawn off during the 24 hour period. This translates to a temperature loss of between 10 to 12 degrees C over the 24 hour period. If 150litres uses 8,7kWh to heat from 20 to 65 deg, standing losses are less than 30% (in my opinion, still much too high).
You would get a 31% saving in heat losses simply by doubling the thickness of the insulation.
The maximum saving by dropping the temperature in the top section by 20 degrees may be (optimistically) around 0,5kWh per day. Say 15kWh per month (= R30 to R40 pm). The average house uses 30kWh per day, so the total saving will only be about 1,5% of the total bill.
BTW, an Xtreme non-ferrous geyser (which is very well insulated) has a temperature drop of about 1 deg/24hrs, so is a lot better than a conventional steel geyser.
Secondly, stratification in a geyser is actually a good thing - it allows the use of the hot water from the top of the tank, while fresh cold water flows into the bottom, and is not allowed to mix with the hot water. This is why many geysers have baffles - specifically to prevent mixing of hot and cold.
AndyD (13-Feb-17)
OK downloaded the report.
I noted an error on table 3, 2nd line, Volume - 30L standard element temperature shows 30, I suspect that this should be 60 Degrees.
I also noted that Under Apparatus it shows that the Econocoil is 3.0KW and the standard element is 3.0KW, however in 5.1 Appendix 1: Heat Distribution Test it shows the Econocoil as 2.0KW and standard element as 3.0KW
I will need time to study the report, just do not have the time right now.
Depending on the Econocoil rating, it may have an influence on the how one interprets the results.
I think I understand what the position of the econocoil is doing, by it's position, improving the distribution of the heat of the water in the geyser due to natural convection movement of heated water, as opposed to the element in the centre.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
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